Psittacosis

Psittacosis is the human disease caused by Chlamydia psittaci, a zoonotic pathogen with a wide host range ^[1]. The organism is described as an obligate intracellular gram-negative bacterium with a unique biphasic developmental cycle ^[1]. In birds it causes avian chlamydiosis, and in humans it causes psittacosis ^[1].

The provided sources characterize psittacosis as part of the atypical pneumonias, which often present as systemic infectious diseases with a pulmonary component rather than as isolated respiratory illness ^[2]. Atypical pneumonias are noted to commonly produce extrapulmonary manifestations, and the pattern of organ involvement may help distinguish them clinically from typical community-acquired pneumonia ^[2]. Source-backed detail on the specific symptom sequence, complications, and severity spectrum of psittacosis itself is not yet available in the snippets ^[2].

Chlamydia psittaci has a wide range of hosts and is zoonotic, indicating an ecology that extends beyond humans and involves animal reservoirs ^[1]. The reviewed literature describes psittacosis as an occupational respiratory infection of interest to NIOSH investigations, suggesting relevance in workplace exposure settings involving animals or environmental sources ^[3]. The supplied sources do not provide numerical burden, regional incidence, or outbreak counts, so those epidemiologic details are not yet available from the evidence provided ^[3][1].

The pathogen is transmitted mainly through horizontal transmission between birds ^[1]. Cross-species transmission can occur, and human-to-human transmission has recently been confirmed ^[1]. Occupational transmission may occur from animals or the environment in relevant settings ^[3].

The provided material identifies occupationally acquired respiratory infections as an important context for psittacosis, indicating elevated relevance in certain jobs and industries ^[3]. It also points to people with animal or environmental exposure relevant to zoonotic transmission, including exposure between birds and cross-species contact ^[1][3]. More specific high-risk groups are not explicitly described in the snippets and are therefore not stated here ^[3][1].

The sources support prevention primarily through exposure control in animal- and occupation-associated settings, with attention to zoonotic and environmental transmission pathways ^[3]. Because human-to-human transmission has been confirmed, prevention should also consider measures appropriate to interrupt onward spread when cases occur ^[1]. Specific prevention protocols, vaccination, and detailed control measures are not stated in the provided snippets ^[3][1].

In surveillance, psittacosis should be interpreted as a zoonotic respiratory infection with potential extrapulmonary features and a strong exposure-history component ^[2][1]. A negative contact history may make zoonotic pneumonias less likely in differential diagnosis, while animal or occupational exposure should raise suspicion in monitoring contexts ^[2][3]. Source-backed detail on laboratory confirmation pathways, reporting thresholds, and standardized case definitions is not yet available from the provided material ^[2].

1. 1 Wang J et al. Chlamydia psittaci: A zoonotic pathogen causing avian chlamydiosis and psittacosis. Virulence. 2024 Dec. PMID: 39541409. doi: 10.1080/21505594.2024.2428411. PubMed: https://pubmed.ncbi.nlm.nih.gov/39541409/
2. 2 Cunha BA et al. The atypical pneumonias: clinical diagnosis and importance. Clin Microbiol Infect. 2006 May. PMID: 16669925. doi: 10.1111/j.1469-0691.2006.01393.x. PubMed: https://pubmed.ncbi.nlm.nih.gov/16669925/
3. 3 de Perio MA et al. Occupational Respiratory Infections. Clin Chest Med. 2020 Dec. PMID: 33153691. doi: 10.1016/j.ccm.2020.08.003. PubMed: https://pubmed.ncbi.nlm.nih.gov/33153691/
4. 4 Psittacosis. Encyclopedic Dictionary of Polymers. 2011. doi: 10.1007/978-1-4419-6247-8_14613. DOI: https://doi.org/10.1007/978-1-4419-6247-8_14613
5. 5 Psittacosis. Tropical Infectious Diseases: Principles, Pathogens and Practice. 2011. doi: 10.1016/b978-0-7020-3935-5.00048-3. DOI: https://doi.org/10.1016/b978-0-7020-3935-5.00048-3
6. 6 Psittacosis. Clinical Guide to Bioweapons and Chemical Agents. None. doi: 10.1007/978-1-84628-787-9_39. DOI: https://doi.org/10.1007/978-1-84628-787-9_39

ICD-10

ICD-11

Total cases

2K

Peak month

2002-06

Coverage

4 reporting countries · 2000-01-01 → 2026-06-20